The rolling door is composed of a plurality of metal sheets which are heavy so that when the rolling door runs downward, a suitable stop mechanism is needed to keep the rolling door running down slowly and stably. Once the normal stop way is functionless, the heavy rolling door running fast could injure people below the door. Therefore, some conventional rolling doors are equipped with an automatic stop mechanism to stop the rolling door when the normal stop mechanism looses its function such as the motor fails. However, these conventional automatic stop mechanisms have a complicated structure and a high price. Furthermore, the conventional automatic stop mechanisms, although can achieve the desired purpose, they are not stable when in use and thus may cause additional problems of the structure of the rolling door such as breaking some parts of the mechanisms.
The present invention intends to provide an automatic stop mechanism which has a simple structure and utilizes the eccentric force when the rolling door runs downward to expand two brake members to stop the door. The structure of the stop mechanism can well mitigate the disadvantages of the conventional stop mechanisms described above.